1. Field of the Invention
The present invention relates to optical and mechanical devices and systems. More specifically, the present invention relates to optical systems used for deep-sea underwater exploration.
2. Description of the Related Art
A variety of cameras are often used to record imagery during deep-sea underwater exploration. Underwater photographers have two basic options for equipment. The first is using an amphibious or waterproof camera such as the Nikonos, which is designed specifically for use underwater. More often, underwater imaging is achieved by putting a traditional film or digital camera into an watertight underwater housing. This allows many more options, since the user can choose a housing specific to their everyday “land” camera, as well as utilize any lens in their collection. For more on this topic, see Wikipedia, the free encyclopedia at http://en.wikipedia.org/wiki/Underwater_photogaphy#Camera_Equipment.
Unfortunately, as is known in the art, certain issues arise when using cameras inside a watertight housing. First, because of refraction, the image coming through the glass port will be distorted, in particular when using wide-angle lenses. The solution is to use a dome-shaped or fish-eye port, which corrects this distortion. Most manufacturers make these dome ports for their housings, often designing them to be used with specific lenses to maximize their effectiveness.
Secondly, some digital cameras do not have sufficiently wide lenses built into the camera. For this reason, many housings are made with supplementary optics in addition to the dome port, making the apparent angle of view wider.
With macro lenses, the distortion caused by refraction is not an issue, so normally a simple flat transparent port is used. In fact, refraction increases the magnification of a macro lens, so this is considered a benefit to the photographer, who may be trying to capture very small subjects.
In any event, the quality of the images acquired depends on the optical performance of the port in the protective housing through which the images are taken.
Conventionally, glass windows have been preferred for this port due to the optical performance thereof. Unfortunately, glass windows tend to be fragile in deep-sea environments due to the high pressures encountered and the typically required points of contact with metal surfaces.
Hence, acrylic windows are typically used in housings for optical instruments used for deep-sea exploration (e.g. at depths approaching 6000 meters under the surface). However, acrylic tends to deform under the high pressures (e.g. approximately 600 atmospheres) encountered in deep-sea exploration. Consequently, a compromise in optical performance has been forced on photographers using acrylic as opposed to glass.
Hence, a need remains in the art for a system or method for improving the performance of high quality optical instruments in high-pressure underwater environments. Specifically, a need remains in the art for a system or method for improving the durability of glass windows used in housing for underwater cameras.